This invention relates to hearing aids, systems for compensating hearing deficiencies of a patient, signal supplying apparatus for use in such systems, and methods for compensating hearing deficiencies. More specifically, the invention relates to hearing aids which can respond to externally supplied electrical signals or generate signals for external use, or both, and to apparatus for externally supplying the electrical signals, and methods of operation of the signal supplying apparatus when connected to a hearing aid.
A person's ability to hear speech and other sounds well enough to understand them is clearly important in employment and many other daily life activities. Professional services which have as their goal to compensate or at least ameliorate hearing deficiencies of hearing impaired persons are consequently important to the community. Unfortunately, such services have in the past been subject to practical difficulties and errors.
For example, in a known approach, the patient's residual hearing has been measured and then a hearing aid has been selected from among different manufacturers and models. The length of time spent in measuring the patient's residual hearing and in selecting a "best" hearing aid from among the different manufacturers and models has been burdensomely long (about two hours). Moreover, the hearing aid selected during the evaluation is often not the actual instrument purchased and then worn by the patient, but is the same model and therefore is representative. Even if a particular hearing aid meets ANSI-1982 specifications, the amplification of the purchased hearing aid instrument can, because of manufacturing variations, differ considerably from that of the trial aid used during the evaluation. Ear canal and earmold effects, which can modify gain and maximum power output by as much as 30 dB, have been difficult to determine precisely and quickly on an individual basis. It has been difficult to accurately measure the patient's residual hearing and the performance of even the trial aid due to assumptions that are conventionally made in calibrating the acoustic characteristics of the audiometer and hearing aids, introducing error into the estimation of sound pressure levels in the patient's ear.
A large amount of information is required in order to simply repeat a particular test condition. Recordkeeping has become difficult and expensive to implement in a reasonable amount of time. And most of the foregoing problems recur should it be necessary to replace a lost or damaged hearing aid.